For many years I had heard of a hardy grapefruit-type tree near Mt.Olive, NC. Last year after becoming very interested in cold hardy citrus, I traced down the owner, Dr. AJ Bullard, and called him and he invited me to visit.
On a cold December day in 2003, I visited him at his home south of Mt, Olive, NC z8a. He has two of the trees which had many grapefruit-size fruit on them and I estimated the trees to be 12-15 feet tall. Dr Bullard informed me that he was given the trees 20 some years ago by someone named Dunstan and that they were a cross between a grapefruit and trifoliate orange. This is thought by some to be what was at one time called the "Dunstan Grapefruit".
In January 1985 and again in December 1989, Dr. Bullard said he recorded minus five degrees at his location. Both of the trees defoliated but recovered and had fruit the following season.
Dr. Bullard allowed me to take fruit and some seedlings from under the tree. I plan to plant some of the seedlings this summer and grow some to larger sizes in the greenhouse. This should make a wonderful ornamental for zone 8 and even though I am not a grapefruit person, the fruit didn't taste half bad.